The infra-structure of imagery can be improved in infants and toddlers through activities.
The answer is, a lot! And we should start as early as possible in the child's life, to take advantage of the fast neural growth rate. Activities that involve imagery will be the name of the game. Here are some ideas, although you probably do many of them already.
Peek-a-boo: Initially, activities that encourage the concept of object permanence are relevant to imagery. Lots of variations of the "Peek-a-boo" game where the child learns that out of sight is not out of existence.
Hide and Seek: Piaget suggests hiding objects, like a bottle or a pacifier, so that a baby can search for them.
In the process of searching, they are demonstrating they have an image or awareness of the object even though it is not in view.
If they do not, they may simply cry or become interested in something else after the object disappears.